91 Z34 still Sick, but now have free scan

[robertisaar]

ALL LQ1s have a FPR that references manifold vacuum.

the pressure jumping as the engine dies is likely the FPR dialing up more pressure since the vacuum in the intake is equal to atmospheric.

the O2 isn't changing since it isn't getting up to a high enough temp to start switching. the only voltage it's showing is the reference voltage from the PCM.

[Schurkey]

1. Far as I know, there is no vacuum hose to the fuel pressure regulator; idle fuel pressure is the same as WFO fuel pressure. Am I not remembering this correctly? Never dealt with a '91, but I'm sure there's no vacuum to the FPR on my '92 and '93.

2. If the fuel pressure is "shooting up 3 to 5 pounds" just as the engine dies, I'd be suspecting a fault in the fuel injector drive system. Computer "forgets" to fire the injectors; or there's an intermittent open in the wiring harness, and there's a surge in fuel pressure because suddenly there's more fuel returning through the regulator.

3. I'm curious as to why the O2 sensor doesn't change voltage much when the engine dies; and why the computer is in open loop unless you turn on the A/C.

[robertisaar]

41PSI at idle? either your FPR(or the vacuum line to it) is junk or you have very little vacuum in the intake... you should be a lot lower at idle, like around 36 or so. only near WOT or key on, engine off should you see close to 43.5PSI.

open loop and closed loop is weather or not the ECM looks at the O2 sensor to correct fueling. closed = uses the O2, open = goes off of VE tables.

you want the ALDL definition.

[portsider44]

do us a favor and get a tunerpro log

it has a LOT more to the stream than what freescan is showing.

will do I downloaded the tunerpro, now do I have to download the $DF ALDL definitions or the $DF Bin definitions or both to get it to work. Please keep in mind while I know a little about computers, but I know very little about running scanner software.

I guess what I am asking is how do I get tunerpro & my car to talk to each other

[portsider44]

well I wnt outside & the beast started so I moved back to the driveway. Killed it & grabbed the computer & fired up freescan again. Attached is the third scan of just driveway idle & some increase idle. I did double check FP & it is still good at 41 idling which is higher than previous time by a fuel. Wonder if it has anything to do with the fact that the FP gauge has been hooked up for over a week. I did notice when I reved motor up which caused it to die, that the fueld pressure would shoot up 3-5lbs as it died?

COuld someone explain open & close loop to me. According to freee scan it is not in closed loop. However when I turned on the A/c the closed loop light lit up on freescan.

[robertisaar]

do us a favor and get a tunerpro log

it has a LOT more to the stream than what freescan is showing.

[portsider44]

The battery has not seem much action as the car has been broke down for over a month. I really don't think the battery is the problem. Main reason for limited reserve is due to all the cranking. It didn't even make it 100 yards before dying & I attemted many restarts trying to get it back to the house.

As for the fuel pressure, it shows 40 lbs key on & it does not drop for several hours. Running it drops to 38lbs & if you rev the motor & it hits the rev limiter it will bounce from 40-43lbs.

Recap of work done:

12/2009 new fuel filter (car stalled so I decided to replace it)

7/2010 Stalled again decided to replace crank postition sensor after doing a little reading on this forum. Before CPS replacement car had didn't have much power. In past it almost felt like you could tell when under light to heavy acceleration that the timing would kick in & the car would get up & go. I also installed new radiator to fix leak, plus new sparkplugs. Car started & seems to run good but still did not have power. Once heated up it would sputter & stall. Sometimes will restart & some time it will not.

Now I can't even get it around the block with out having problems? Can't say that I have heard any audible pings. I think I will put it back on the charger & see how long it will idle while with the freescan running. Normally it will idle for some time with out dying

[Schurkey]

1. Still don't have the battery fully charged; OR the battery is defective--no reserve capacity. That or you're doing a LOT of cranking.

2. I find it interesting that the O2 sensor shows about the same reading when the engine is running as when it's not.

3. What is your fuel pressure when the engine dies? I don't see a fuel trim column in your excell sheet.

4. I don't think you have a problem with the timing. Yeah, it's 40+ degrees of advance; but the computer is simulating both centrifugal and vacuum advance; and you aren't complaining about audible "ping".



Your description of this problem is sounding a lot like what happened to my '93 Lumina when the fuel pump was on it's last legs--no power, engine dies, sometimes restarts easily--sometimes not.

[portsider44]

Ok guys put the charger on this morning & let ie charge for a little over 4 hours. Unlike my first scan this is on a totally cold start. Last time it took a while to get free scan going. SO by the time I did get it going car had been running.

So hook up lap top, fire up free scan key on & scanning started. Car fires up on first attempt & doesn't die. Then attempt to take around the block. Back out of driveway & drive 100 ft make a right turn & start to build speed. Car has no power, but no shake or bad miss. Don't make it 100 yards before it just dies.

I am able to restart & make u turn by dies quickly. Followed by several restarts & quick stalls, had to push it the last 30 foot to get it in front of the house.

Battery volts looked good at 1st but after all the cranking it dropped again. What should the sprak advance be? still seems high to me.

[Schurkey]

So you the rest of the numbers looked fine?

I'm not saying that. I'm saying that the reason things are goofy MIGHT be nothing more than a dying battery. Charge and re-test.

[robertisaar]

more scans is better, you can never have too much information.

[portsider44]

So you the rest of the numbers looked fine? Car kept dying which resulted in a lot of cracking in attempt to restart, which did discharge the battery. However when running volts ran in the 13.5, however at times when at idle turning on a/c would casue it to stall.

Not knowing what the numbers should be at the numbers that seem odd to me was the spark advance. During cranking it would be 50+, while running would be in the 20-40 range. Is this normal or a sign that my ICM is faulty.

Also is it normal to have Knock counts w/o any knock retard?

Also at times 02 counts looked odd, however it could just be do to going from running to dying? Woould another scan / test run help? I can charge the battery & try again?

[Schurkey]

I'd charge the battery.

At 0 rpm, you've got something like 12 volts. Battery is very discharged.

[robertisaar]

IMO, tunerpro has too many advatages over freescan to use it.

[portsider44]

Ok so I logged to csv & put it in excel file. Here is the results of trying to go around the block on a test drive. I highlighted in yellow when the car died. Still no power, almost didn't make it back, just kept stalling. Feel free to ask questions, I would love to get this resovled this weekend if all possible.